The cutter links or cutter teeth, as they are also known, of a standard chainsaw chain include a depth gauge and a cutter edge separated by a space. The cutter edge is normally sharpened or filed by use of a round file. One of the main difficulties involved in the sharpening of the cutting edges is the problem of maintaining uniformity in the curved cutting edges of the cutter teeth.
Devices have been developed for holding round files for sharpening the cutter edges of the cutter teeth. An example is found in U.S. Pat. No. 2,737,830 (Siverson et al.) which discloses a filing guide with a longitudinally extending slot therein, the slot enabling the guide to be placed around the tooth on the saw chain. Another example is U.S. Pat. No. 3,365,805 (Carlton) which discloses a saw chain filing guide comprising a flat plate having a slot to straddle a depth gauge and side plate on a cutter tooth to be sharpened. U.S. Pat. No. 4,473,958 (Atkinson) discloses a filing guide having a first slot adapted to receive the depth gauge and a second slot adapted to receive a safety projection.
Other patents of general interest are U.S. Pat. Nos. 4,412,463 (Beerens), 4,438,667 (Hannah), 3,283,615 (Kephart, Jr.), 4,228,702 (Stewart et al.), 3,670,600 (Arff), 3,438,286 (Silvon), 4,404,872 (Fritz) and 3,733,933 (Longbrake).
The prior art does not offer a solution which permits simple filing in the conventional manner where both hands are used on the file and without the need for holding a depth gauge of some kind and which can be used on essentially all chainsaw chains having a common pitch.
The prior art also does not offer a simple device which holds a round file in the proper position to file the cutter teeth and wherein the guide prevents the file from filing down into the inner links.